[Top] [All Lists]

Re: [TowerTalk] Windings on Amidon core

Subject: Re: [TowerTalk] Windings on Amidon core
From: Ian White G/GM3SEK <>
Reply-to: Ian White GM3SEK <>
Date: Fri, 12 Aug 2005 08:23:46 +0100
List-post: <>
jan elburg wrote:
>Dear Fellow TowerTalkers,
>Trying to make a hybrid coupler (collins method) for 2 phased verticals.
>Found a recipe in ON4UN's Low Band Handbook.
>And what seemed an easy calculation, regarding the number of turns, is
>keeping me puzzled.
>The used componets : 1 Amidon T225 core a a piece of copper wire.
>The inductance should be 1.13uH for 7 mc/s.
>Formula  L= 50/ 2*3.14*7.05
>According to the formula for calculating the number of turns, in my case
>for 7 mc/s, it turned out to
>9,7 turns making 10 turns.
>Formula N = 100 * square root 1.13 / 120
May I recommend DL5SWB's Mini Ring Core Calculator?

It has a large library of core data from many different manufacturers, 
including dimensions and paint color as an identity check.

If your core genuinely is a T225-2, your calculation of 9.7 turns looks 

>10 turns on the T225 core gave 2,50 uH in stead of the desired 1.13 uH.
>Measured with my MFJ259B.
>I don't expect the MFJ very accurate, but 100 % off, I don't believe.
Sorry , I don't have one (Tom?) but a measurement based on 
series/parallel resonance should be more accurate.

73 from Ian G/GM3SEK         'In Practice' columnist for RadCom (RSGB)

See:  for "Self Supporting Towers", "Wireless Weather 
Stations", and lot's more.  Call Toll Free, 1-800-333-9041 with any questions 
and ask for Sherman, W2FLA.

TowerTalk mailing list

<Prev in Thread] Current Thread [Next in Thread>